The alleged Nigerian mastermind of the kidnapping of a Briton and an Italian killed last week amid a rescue attempt has died of gunshot wounds from his arrest, police said Wednesday.

The man, Abu Mohammed, was wounded and detained in a March 7 raid in the town of Zaria, one day before the British-Nigerian rescue attempt of the two European men, who had been in captivity for almost one year, police said.

Mohammed died on March 9 -- one day after the failed hostage rescue attempt in the northwestern city of Sokoto -- "following severe bullet wounds sustained" during his arrest, Nigeria's secret police said in a statement.

Police also blamed Islamist sect Boko Haram for kidnapping the men, saying that "investigations revealed that the plot was masterminded by the Abu Mohammed-led faction of Boko Haram in Nigeria".

The initial raid yielded information on the hostages' whereabouts -- but it also imperilled them because one extremist escaped and apparently alerted the guards who killed the foreigners "before the arrival of security forces".

"Preliminary interrogations of the arrested suspects revealed that the guards protecting the two foreign hostages in Sokoto had been directed to kill them in the event of any envisaged threat," it said.

The statement added: "The arrested suspects therefore advised that a rescue operation be immediately initiated, moreso as one of them had escaped during the Zaria raid."